A new fin and fin blade

ABSTRACT

A fin blade for free diving or swimming or scuba diving is described, which has a cross section at one end angled about a yaw, or longitudinal, axis relative to the cross section at the other end. The arrangement is such that a lateral line at a proximal end is disposed at an angle relative to a lateral line at a portion spaced from the proximal end. The fin blade is more closely aligned with the ergonomic complexities of the human body, such that during finning the fin blade provides greater comfort and/or propulsion. A fin blade is also described which includes a reinforced zone in one portion of the fin blade, such that one portion of the blade at the distal end is relatively increased in flexibility to provide a catch zone at one portion of the distal end of the fin blade.

CROSS-REFERENCE TO RELATED APPLICATIONS

1a. This application is a national phase application under 35 U.S.C. §371 of PCT/AU2021/050345 filed Apr. 19, 2021 entitled “A NEW FIN AND FINBLADE,” which claims the benefit of and priority to Australian PatentApplication No. 2020901227 filed Apr. 17, 2020, the contents of both ofwhich being incorporated by reference in their entireties herein.

TECHNICAL FIELD

1. The present technology relates generally to diving fins, includingscuba diving fins, free diving fin assemblies, scuba diving finassemblies, scuba diving fin blades and free diving fin blades.

BACKGROUND

2. Diving is very popular. The sense of peace and freedom to be foundwhen underwater is highly rated among participants. The presenttechnology finds efficient application in any form of diving. Theremainder of the specification, however, will discuss freediving.Freediving in particular, is an underwater multi-discipline sport thatis characterized by breath-holding diving; while freediving, divers donot use scuba equipment to provide air while underwater. Freedivingincludes spearfishing, underwater hockey, underwater rugby, snorkeling,apnea and competitive apnea.

3. Competitive apnea takes a myriad of forms: Constant weight apnea,dynamic apnea, jump blue, variable weight apnea. In these competitions,divers look for maximum efficiency from their fins.

4. There is a myriad array of fins available. Basically there are thoseof unified construction, in which all components may be glued togetheror molded together as one unit, and those of multi-part construction, inwhich the fin may be readily disassembled into its component parts byuse of a screwdriver or Allen key or like tool. Disassembly may even betool-less.

5. Component parts of fins include foot pocket and blades. In themulti-part fin designs, the blades are detachable from, or at leastinsertable into, the fin pocket.

The blades fit into the foot pocket by insertion of a tongue, and thetongue is held in the foot pocket by fastening screws, even glue. Thetongue can be angled, usually downwards, to provide certain advantagesof finning efficiency, perhaps when a diver is on the surface, and evento provide a particular ergonomic advantage when finning horizontally orvertically.

6. The present technology seeks to ameliorate one or more of the abovementioned disadvantages, and/or to provide a finning efficiencyimprovement over known fins and fin blades, by seeking to provide acloser alignment of the fin to the mechanics of a diver's body.

SUMMARY

7. Broadly, the present technology provides a free diving fin bladewhich is angled and/or twisted about a yaw, or longitudinal, axis.

8. Broadly, the present technology provides a free diving fin whichincludes a blade angled and/or twisted about a yaw, or longitudinal,axis.

9. Advantageously, it is believed that the present technology provides afree diving fin which is more closely aligned with the ergonomiccomplexities of the human body than known fins, such that during finning(the diving term for kicking along, up or down, with the legs whilewearing fins on the feet) the blade provides greater comfort and/orpropulsion than known fins.

10. In accordance with one aspect of the present disclosure there isprovided a free diving fin blade including a main portion twisted fromone end to the other about a yaw, or longitudinal, axis.

11. In accordance with another aspect of the present disclosure there isprovided a free diving fin blade where the fin blade cross section atone end is disposed at an angle relative to the cross section at theother end.

12. In accordance with yet another aspect of the present disclosurethere is provided a free diving fin blade wherein a lateral line at aproximal end is disposed at an angle relative to a lateral line at aportion spaced from the proximal end.

13. In accordance with still another aspect of the present disclosurethere is provided a free diving fin blade wherein a line from rail torail at one end is disposed at an angle relative to a line from rail torail at the other end.

14. In accordance with a yet further aspect of the present disclosurethere is provided a free diving fin which includes a blade which istwisted about a longitudinal or yaw axis.

15. In one embodiment the blade includes a tongue for connecting a mainblade portion to a foot pocket.

16. In one embodiment the main blade portion is angled downwardlyrelative to the tongue to facilitate comfort when finning on the watersurface and for ergonomic comfort generally underwater, finning up, downor along.

17. In one embodiment the tongue is angled downwardly, (about a rollaxis or substantially lateral line) relative to the main blade portionfor increased comfort and efficiency when finning.

18. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 1 and 45 degrees.

19. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 2 and 20 degrees.

20. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 2 and 22 degrees.

21. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 2 and 23 degrees.

22. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 2 and 26 degrees.

23. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 3 and 30 degrees.

24. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 3 and 33 degrees.

25. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 3 and 35 degrees.

26. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 2 and 30 degrees.

27. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 2 and 10 degrees.

28. In one embodiment the main blade portion is angled relative to thetongue downwardly by between 2 and 5 degrees.

29. In one embodiment the main blade portion is angled relative to thetongue downwardly by about 2.25 degrees.

30. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by between 1 and 50 mm.

31. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by between 2 and 20 mm.

32. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by between 5 and 10 mm.

33. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by between 2 and 35 mm.

34. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by between 3 and 15 mm.

35. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by between 5 and 10 mm.

36. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by about 5 mm.

37. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by about 4 mm.

38. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by about 3 mm.

39. In one embodiment the lateral line at the proximal end is elevatedfrom one side to the other by about 10 mm.

40. In one embodiment the main blade portion is substantially planar inshape.

41. In one embodiment the main blade portion includes rails to inhibitvortices forming, or simply to channel water along the blade moreeffectively for greater efficiency of finning. The rails also facilitateincreased stiffness of the main blade portion.

42. In one embodiment the blade twist commences at a lateral joinbetween the tongue and the main blade portion.

43. In one embodiment the blade twist is twisted inwards to suit certaindivers' ergonomic mechanics.

44. In one embodiment the blade twist is twisted outwards to suitcertain divers' ergonomic mechanics.

45. In one embodiment the lateral line between the tongue and the mainblade portion is disposed at an angle about an axis normal to the mainblade surface.

46. In one embodiment the angle of the lateral line is between about 5and 45 degrees.

47. In one embodiment the angle of the lateral line is 2.25 degrees.

48. In one embodiment the angle of the lateral line is 1.5 degrees.

49. In one embodiment the angle of the lateral line is 2.5 degrees.

50. In one embodiment the angle of the lateral line is 3 degrees.

51. In one embodiment the angle of the lateral line is 4 degrees.

52. In one embodiment the angle of the lateral line is 5 degrees.

53. In one embodiment the angle of the lateral line is 6 degrees.

54. In one embodiment the angle of the lateral line is 7 degrees.

55. In one embodiment the angle of the lateral line is 8 degrees.

56. In one embodiment the angle of the lateral line is 9 degrees.

57. In one embodiment there is a radius on the lateral edges of theblade to reduce stresses. In one embodiment the radius is about 50 mm.

58. In one embodiment the tail end of the main blade portion is a fishtail shape.

59. In one embodiment the tail end of the main blade portion is a jettail shape.

60. In one embodiment the tail end of the main blade portion is aswallowtail shape.

61. In one embodiment the tail end of the main blade portion is rounded.

62. In accordance with another aspect of the present disclosure there isprovided a fin blade for freediving which includes a flexible matrix,and a reinforced zone disposed on the flexible matrix in a regionproximal a foot pocket and adjacent at least a portion of an edge of theproximal region.

63. In an embodiment the reinforced zone is disposed adjacent at least aportion of an outer edge of the proximal region.

64. In an embodiment the reinforced zone is disposed adjacent at least aportion of an inner edge of the proximal region.

65. In an embodiment the main blade portion includes a flexible matrix,and a reinforced zone disposed on the flexible matrix in a regionproximal both a foot pocket and extending along at least a portion of anouter rail.

66. In an embodiment the main blade portion includes a flexible matrix,and a reinforced zone disposed on the flexible matrix in a regionproximal both a foot pocket and extending along at least a portion of aninner rail

67. In an embodiment the reinforced zone is disposed in a substantiallytriangular region at a proximal end near a foot pocket, bounded by aline from an inner end of a proximal region to an intermediate pointalong an outer edge of the main blade portion.

68. In an embodiment the reinforced zone is disposed in a substantiallytriangular region at a proximal end near a foot pocket, bounded by aline from an outer end of a proximal region to an intermediate pointalong an inner edge of the main blade portion.

69. In an embodiment the substantially triangular region of thereinforced zone includes curved edges.

70. In an embodiment there is provided a flexible catch zone, adjacentthe reinforced zone, which is generally comprised of only the flexiblematrix.

71. In some embodiments the reinforced zone includes a layup of about anadditional 200 g balance strength carbon fiber matting to provide thereduced flex in the outer zone along the outer edge and proximal thelocation of the outer toes would be in the fin assembly when fitted to auser.

72. In some embodiments the reinforced zone includes a layup of about anadditional 200 g balance strength carbon fiber matting to provide thereduced flex in the inner zone along the inner edge and proximal thelocation of the inner toes would be in the fin assembly when fitted to auser.

Clarifications

73. In this specification, where a document, act or item of knowledge isreferred to or discussed, this reference or discussion is not anadmission that the document, act or item of knowledge or any combinationthereof was at the priority date:

-   -   (a) part of common general knowledge; or    -   (b) known to be relevant to an attempt to solve any problem with        which this specification is concerned.

74. It is to be noted that, throughout the description and claims ofthis specification, the word ‘comprise’ and variations of the word, suchas ‘comprising’ and ‘comprises’, is not intended to exclude othervariants or additional components, integers or steps.

BRIEF DESCRIPTION OF THE DRAWINGS

75. In order to enable a clearer understanding, an embodiment of thetechnology will now be further explained and illustrated by reference tothe accompanying drawings, in which:

76. FIG. 1 is a tail or distal end elevation view of a prototype finblade with lateral construction lines showing the twist in the blade;

77. FIG. 2 is an isometric view from underneath and the distal or tailend of two free diving fin blades, one closest to the viewer being thefin blade of an embodiment of the present technology, having twist abouta longitudinal or yaw axis, and the fin blade underneath with its edgesonly shown, being a known embodiment with no blade twist;

78. FIG. 3 is an isometric view from the proximal or tongue end of thetwo fins shown in FIG. 2 ;

79. FIG. 4 is a tail elevation view of the fin blade shown in FIG. 1 ,but shown with the other one in the pair. The lift on the inside edge ofthe fin blade at the tongue end can be seen, which causes the main bladeportion to twist;

80. FIG. 5 is a side elevation section view of the proximal end of theblade, showing the comparison between the known and the new embodiments,with one lateral edge adjacent the tongue being higher than the otherlateral edge in the new blade, by 5 mm;

81. FIG. 6 a plan view of two different sizes of the two blades of anembodiment of the present technology. FIG. 6 a is a shorter fin blade,about 500 mm long, and FIG. 6 b is a longer blade, about 635 mm long;

82. FIG. 7 is an isometric view from underneath of a pair of fin bladesin accordance with an embodiment of the present disclosure, showingconstruction of strengthened zones for increased stiffness, and weakerzones for increased catch;

83. FIG. 8 is a perspective view from the tail end of two fin bladesshown in FIG. 7 , showing the strengthened (outer) and relativelyweakened zones (inner);

84. FIG. 9 is a perspective view from the tail end of two fin blades,similar to those shown in FIGS. 7 and 8 , but which have been flipped,so that the strengthened zones are proximal the inner edges;

85. FIG. 10 is a perspective view of a pair if foot pockets with framesfor receiving the fin blades;

86. FIG. 11 is a detail of a fin frame rail which shows the profiledsection for receiving the fin blades;

87. FIG. 12 is a partial exploded view of a pair of fin blades, adjacentthe fin frame rails; and

88. FIG. 13 is a perspective view of an assembled pair of fins whereinthe foot pockets and frames from FIG. 10 are joined to the fin bladesfrom the other Figures.

DETAILED DESCRIPTION

89. Referring to the drawings there is shown an embodiment of freediving fin blade generally indicated at 10. The fin blade 10 is angledand/or twisted along at least a portion of its length about a yaw, orlongitudinal, axis as shown in at least FIG. 1 . The fin blade 10 isconfigured to fit into a foot pocket 90 of a fin frame so as to form acomplete fin assembly shown in FIG. 13 . The fin blade 10 may be gluedor otherwise fastened into place in rails 99 of a foot pocket 90, or thefin blade 10 may be molded to form a unified fin which cannot bedisassembled.

90. The fin blade 10 includes a tongue 20 integral with or connected toa main blade portion 22. The tongue 20 when the fin blade 10 isassembled into the foot pocket 90, fits under the foot receiver 92.

-   -   Yaw Angle—Twisted Main Blade

91. It can be seen in the Figures that the free diving fin blade 10 hasa cross section at the proximal end 12 which is disposed at an anglerelative to the cross section at the distal end 14. To make this moreclear, it can be seen that a lateral line 13 which extends across thefin blade 10 at the proximal end 12, is disposed at an angle relative toa lateral line 15 extending across the fin blade 10 at the distal end14. Again, in a hope to make it even more clear, it should be understoodthat the lateral line 13, 14 may be disposed anywhere along the blade,and as long as the two lateral lines 13,14 are spaced some distanceapart, the twist may occur anywhere along the blade 10, for any suitablelength.

92. The main blade portion 22 may be twisted such that the two laterallines 13 and 14 are angled relative to each other by between 0.5 and 45degrees. Most usefully it seems that the twist angle is about 2.25degrees as shown in the Figures, but depending on the ergonomics of theuser, the twist angle may be between 2 and 20 degrees, or between 10 and20 degrees, or between 15 and 20 degrees, or by between 25 and 30degrees, or between 0.5 and 1 degrees, or between 1 and 2 degrees, orbetween 2 and 3 degrees. The twist angle may be 2, 2.25, 2.25, 2.75, 3,3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20degrees depending on the ergonomics of the intended user.

93. It can be seen that the 2.25 degree twist shown in the Figuresresults in one end 18 of the lateral line 13 at the end adjacent thetongue 20 (or proximal end) is elevated relative to the other end 19 ofthe lateral line 13 by about 5 mm. This does depend on the width of themain blade portion 22. In other embodiments, although not shown, it isto be understood that good performance and comfort can be obtained whenthe elevation is between 1 and 50 mm, or between 2 and 35 mm, or between5 and 10 mm. The elevation of the end 18 of the lateral line maytherefore be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm to provide goodcomfort and performance depending on the ergonomics of the intendeduser.

94. It is believed that at least the abovementioned twist angle, and/orthe features described below, of the free diving fin blade 10 of theembodiment shown provides a fin which is more closely aligned with theergonomic complexities of the human body, such that during finning (thediving term for kicking along, up or down, with the legs while wearingfins on the feet) the blade provides more comfort and/or greaterpropulsion than known fins.

-   -   Construction of Fin Blade

95. Turning to FIGS. 7 and 8 , an example construction of fin blades 10is shown.

96. The blades are constructed from carbon fiber, but they may equallywell be constructed from polymer or fiberglass or other suitablematerial.

97. The fin blades 10 in the embodiment shown are constructed fromcarbon fiber, and includes a carbon fiber matrix 38 with a reinforcedzone 40 and a catch zone 45, which is more flexible. The reinforced zone40 is disposed in a region generally encompassing the tongue 20, andextending into an outer zone of the fin blade proximal the outer toes,and along at least a portion of an outer edge 23 of each fin blade 10.

98. Generally speaking, an inner edge 25 is free from reinforcement, andincludes only the matrix 38, which is a blade of flexible carbon fibermat with suitable resin. In this way, it is considered that the inneredge 25 should be more flexible than the outer edge 23 so that the innerregion at the tail or distal end 14 functions as a catch zone. In thismanner the whole blade is believed to operate more efficiently thanknown blades where the whole blade flexes and catches evenly across thewhole width of the blade.

99. In some constructions the reinforced zone 40 includes a layup ofadditional 200 g balance strength carbon fiber matting to provide thereduced flex in the outer zone along the outer edge 23 and proximalwhere the outer toes would be in the fin assembly at 19, when fitted toa user. This construction, stiffer on the outer, proximal end (towards19 and 23), contributes to a more efficient catch and propulsion overknown fin blades. In combination with the twisted angle, there isbelieved to be increased ergonomic matching, comfort and power whenfinning.

100. The reinforced zone 40 on the main blade portion 22 is confinedsubstantially in the embodiment shown to a triangular area bounded by aline from 18 to an intermediate point 27 along the outer edge 23 of themain blade portion 22. The intermediate point 27 may be any suitabledistance from the distal end 14, say 10 mm, 20 mm, 30 mm, 40 mm, 50 mm,60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm, 150mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, 210 mm, 230 mm, 240 mm, 250mm, 260 mm, 270 mm, 280 mm, 290 mm or 300 mm.

-   -   Roll Angle—Tongue/Blade

101. It can be seen from the drawings that the tongue 20 is also angled(about a roll axis or substantially lateral line, say, line 13 in thedrawings) relative to the main blade portion 22 for increased comfortand efficiency when finning. The main blade portion 22 is angleddownward relative to the tongue 20 to facilitate finning on the surface,and for ergonomic finning when ascending or descending.

102. The main blade portion 22 may be angled relative to the tongueupwardly or downwardly by between 1 and 45 degrees. While the Figuresshow about 30 degrees is probably optimal, the roll angle may be 2, 5,6, 7, 8, 9, 10, 13, 15, 17, 20, 22, 25, 27, 30, 35, 40 or 45 degrees,depending on the technique of the proposed user.

-   -   Fin Assembly

103. The tongue 20 and main blade portion 22 are substantially planar inshape, for ease of fitment into a fin pocket 90.

104. The main blade portion 22 is configured to be inserted into framerails 99 which have some height above the planar surface of the mainblade portion 22, to inhibit vortices forming, or simply to channelwater along the blade more effectively for greater efficiency offinning. The rails 99 also facilitate increased stiffness of the mainblade portion.

-   -   Further Clarifications

105. Modifications and improvements to the disclosure will be readilyapparent to those skilled in the art. Such modifications andimprovements are intended to be within the scope of this disclosure.

Advantages

106. Advantageously, embodiments of the apparatus provide improvedmatching of the fin to suit the ergonomic mechanics of selected diversfor greater efficiency of finning.

107. The triangle shape of the reinforced zone is one way of naturallyproviding a gradient of stiffness from relatively strong at the proximalend line 13 to less strength at the distal end line 14. It is believedthat a torsion force is provided by the arrangement from the proximalend line 13 to the fin tip line 14 to let the soft part catch morewater.

108. The fin blade pair can be arranged in the fin pocket 90 so that thereinforced area is on the outer edge, and this suits a small kick,allowing a user to kick for longer time at increased efficiency. Theswing of the body from left to right is bigger, so the fin's functionalsurfaces also bigger, then it's more efficient.

109. When the blade pair is arranged in the fin pocket 90 so that thereinforced area is disposed on the inner edge, this is suitable for amore powerful kick. The swing from left to right on the body during afinning stroke, can be lower, which lets the user place more focus ontheir kick to push the performance. This also mimics mono fin trainingbut provides more flexibility of movement than monofin training, freeingup the legs and reduces the claustrophobia and uncertainty associatedwith monofin training.

1. A fin blade suitable for free diving wherein a lateral line adjacenta proximal end of the fin blade is disposed at an angle relative to alateral line at a portion spaced from the proximal end of the fin blade,and wherein the lateral line at the proximal end of the fin blade iselevated from one side to the other.
 2. The fin blade in accordance withclaim 1 wherein the lateral lines extend from rail to rail so thatsubstantially the whole cross section of the blade is twisted at one endrelative to the other.
 3. The fin blade in accordance with claim 1wherein the blade comprises a tongue for connecting a main blade portionto a foot pocket.
 4. The fin blade in accordance with claim 3 whereinthe fin blade comprises a main blade portion which is angled downwardlyrelative to the tongue between 1 and 45 degrees to facilitate comfortwhen finning on the water surface and for ergonomic comfort generallyunderwater, finning up, down or along.
 5. The fin blade in accordancewith claim 1 wherein the lateral line at the proximal end is elevatedfrom one side to the other by between 1 and 50 mm.
 6. The fin blade inaccordance with claim 4 wherein the lateral line at the proximal end iselevated from one side to the other by about 5 or 10 mm.
 7. The finblade in accordance with claim 3 wherein the main blade portion issubstantially planar in shape.
 8. The fin blade in accordance with claim3 wherein the main blade portion comprises rails to inhibit vorticesforming, or simply to channel water along the blade more effectively forgreater efficiency of finning.
 9. The fin blade in accordance with claim3 wherein the proximal lateral line extends laterally at a lateral joinbetween the tongue and the main blade portion.
 10. The fin blade inaccordance with claim 3 wherein the lateral line elevation at the oneend causes the main blade portion to twist inwards to suit certaindivers' ergonomic mechanics.
 11. The fin blade in accordance with claim3 wherein the lateral line elevation at the one end causes the mainblade portion to twist outwards to suit other divers' ergonomicmechanics.
 12. The fin blade in accordance with claim 1 wherein theelevation of the lateral line at the one end causes the relative angleof the lateral lines to be between about 2 and 45 degrees.
 13. The finblade in accordance with claim 1 wherein the angle of the lateral lineis about 2.25 to 6 degrees.
 14. The fin blade in accordance with claim 3wherein the main blade portion comprises a flexible matrix, and areinforced zone disposed on the flexible matrix in a region proximalboth a foot pocket and extending along at least a portion of one edge,extending towards the distal end.
 15. The fin blade in accordance withclaim 14 wherein the reinforced zone is disposed in a substantiallytriangular region at a proximal end near a foot pocket, bounded by aline from one end at one edge of a proximal region to an intermediatepoint along the other edge of the main blade portion.
 16. The fin bladein accordance with claim 15 wherein the substantially triangular regionof the reinforced zone comprises curved edges.
 17. The fin blade inaccordance with claim 14 wherein there is provided a flexible catchzone, adjacent the reinforced zone on the distal end thereof, which isgenerally comprised of only the flexible matrix.
 18. The fin blade inaccordance with claim 17 wherein the flexible catch zone is disposed inan inner edge region of the distal end when in a pair.
 19. The fin bladein accordance with claim 17 wherein the flexible catch zone is disposedin an outer edge region of the distal end when in a pair.
 20. The finblade in accordance with claim 14 wherein the reinforced zone comprisesa layup of about an additional 200 g balance strength carbon fibermatting to provide the reduced flex in the reinforced zone.
 21. A fin orfin assembly for free diving which includes a comprises the fin blade inaccordance with claim 1, the fin blade fastened to or integral with afin pocket.
 22. A fin blade for freediving, comprising: a flexiblematrix and a reinforced zone disposed on the flexible matrix in a regionproximal a foot pocket and adjacent at least a portion of an outer edgeof the proximal region, wherein a lateral line adjacent a proximal endof the fin blade is disposed at an angle relative to a lateral line at aportion spaced from the proximal end of the fin blade, and wherein thelateral line at the proximal end of the fin blade is elevated from oneside to the other.
 23. A fin suitable for free diving, comprising: afoot receiver and a blade, the blade being configured to fit into thefoot receiver, wherein a lateral line adjacent a proximal end of theblade is disposed at an angle relative to a lateral line at a portionspaced from the proximal end of the blade, and wherein the lateral lineat the proximal end of the blade is elevated from one side to the other.